CH. Ill] A CONSIDERATION OF THE EVIDENCE 31 



patients suflFering from scarlet fever. 'The bacilli were present 

 in 32 out of a series of 40 cases examined and sometimes 

 greatly outnumbered the other organisms present. 



Lustgarten's bacillus (1884) in syphilis and Sanarelli's 

 JBac. icteroides (1897) in the case of yellow fever may be 

 quoted as examples of secondary invaders to the presence of 

 which diseases were wrongly attributed, and many other 

 instances might be given. 



Bacteria may he present in healthy organs. Ford (1900) 

 examined the liver and kidneys of healthy animals after death 

 with the most stringent precautions against contamination 

 and found that at least 80 per cent, contained bacteria of 

 various kinds. 



Dudgeon (1908) states that staphylococcus albus can be 

 cultivated from the great omentum in many healthy animals 

 and quotes many examples to show that pathogenic organisms 

 can exist in the body for long periods without giving rise to 

 any symptoms. Savage (1907-8) has recorded the presence of 

 B. Gasrtner in the intestines of healthy young calves. Zwich 

 and Weichel (1910) found that out of 177 healthy mice, 28 

 contained B. Aertrych in their faeces. 



Post mortem invasion must be guarded against, for after 

 the death of an animal secondary infection is extremely likely 

 to occur. Dudgeon and Sargent (1907) record a case of 

 pneumococcal peritonitis in man, in which the peritoneal 

 exudate one hour after death gave a pure culture of pneu- 

 mococci, whereas 26 hours later B. coli alone could be 

 recognised in the same exudate. 



4. The repetition of an experiment with an identical 

 result as regards the variation produced is valuable con- 

 firmatory evidence, particularly in the hands of difiFerent 

 investigators. Inability to repeat the phenomenon, though 

 by no means disproving its original occurrence, does to some 

 extent discredit it. 



5. The constancy of the new feature, particularly on 

 subculture, is of importance both as enabling one to exclude 

 various errors of observation and as indicating the funda- 

 mental character of the change. On the other hand a tendency 



